An ever sparser supply of metal ore, particularly iron ore makes it increasingly important to salvage old and surplus metal structures. When the structures are relatively small, such as metal shavings and the like, there is little problem in salvaging and reusing them as scrap metal. Even larger structures such as passenger automobiles are readily salvaged by placing them in presses and compacting them into small compressed metal packages which are then forwarded to a steel mill for remelting and manufacture into steel ingots and the like.
However, when the structures become larger their salvage becomes more difficult since it is normally impossible to ship them to and use them in a steel mill due to their bulk and weight. They must therefore be cut or severed into smaller, more readily handled pieces. The salvage of large ocean-going vessels and railroad cars, for example, requires that the structure be cut up in the field and shipped to the mill before they can be melted.
In the past such a structure, say a vessel, was salvaged by systematically dismantling it, i.e., by torch or flame cutting it into smaller components. Conventional hoisting equipment such as a crane then lifts the components, say a portion of the vessel's bridge or a section of its hull on land where the component is further cut down in size with torch cutting equipment or, to the extent presses are available by shearing the components into relatively small pieces of scrap metal. In instances where the vessel is not too far from a factory which has an industrial shear available, it is also common to transport the dismantled components to the factory and there shear them into small scrap metal pieces.
The ever-increasing price of scrap metal now makes such methods economically more feasible even though they require much manpower and consume large amounts of expensive cutting gas. Furthermore, the commonly encountered heavy layer or layers of paint, rust, organic or inorganic substances such as scum, barnacles, etc. on vessels being salvaged can make torch cutting difficult if not impossible. Conventional torch cutting equipment cannot cut through heavy layers of rust, scum or paint and the paint has a tendency to sputter and generates so much smoke that it may impair the cutting operation, speed and accuracy. Thus, the rust, paint, etc. is ordinarily first scraped or burned off along the cutting line before the actual torch cutting commences to eliminate the mentioned problems and hazards.
Moreover, after the relatively large component has been dismantled and transferred on dock or land, it must further be cut down in size to become scrap metal that is accepted by steel mills. Additionally, smaller size scrap yields higher scrap metal prices; it is therefore desirable to cut the component into the smallest possible pieces subject only to limitations caused by the unit cutting costs. Thus, by the time the vessel has been cut down to acceptably small pieces of scrap metal, the unit cost of the scrap metal is relatively high and/or the sales price for the scrap is relatively low. Profit margins are therefore small which discourages the wisest possible salvage of old, surplus vessels and other metal structures. This in turn adversely affects the raw material supply and, in time, will necessarily tend to increase metal costs.